Sipuncula facts for kids

Quick facts for kids Sipuncula Temporal range: Cambrian–Recent PreЄ Є O S D C P T J K Pg N
Thysanocardia nigra
Scientific classification
Classes, orders and families
Class Phascolosomatidea Order Aspidosiphonida Family Aspidosiphonidae Order Phascolosomatida Family Phascolosomatidae Class Sipunculidea Order Golfingiida Family Golfingiidae Family Phascolionidae Family Sipunculidae Family Themistidae

Sipuncula

The Sipuncula, also known as peanut worms, are a small group of worms that live in the ocean. Scientists sometimes call them a phylum (a major group of animals) or a class within the Annelida (segmented worms). There are between 144 and 320 different kinds, or species, of these worms. Peanut worms have bodies that are symmetrical, meaning they can be divided into two matching halves. Unlike some other worms, their bodies are not divided into segments.

What Do Peanut Worms Look Like?

Peanut worms are shaped like worms and can be very small, from about 2 millimeters (the size of a tiny ant) up to 720 millimeters (almost 30 inches) long. Most species are shorter than 10 centimeters (about 4 inches). Their body has two main parts: a thin front section called the introvert and a larger main body section called the trunk. The introvert can be pulled back into the trunk, much like a turtle pulling its head into its shell.

Peanut worms have a special body cavity called a coelom. Their body wall is strong and muscular, similar to that of annelid worms. When these worms feel threatened, they can pull their bodies into a tight, round shape that looks a lot like a peanut kernel. This is how they got their common name, "peanut worm."

The Introvert: A Special Head Part

The most unique part of a peanut worm is its mouth. It is surrounded by 18 to 24 ciliated tentacles. These tentacles have tiny hair-like structures called cilia. The worm can pull all of these tentacles inside its body.

Peanut worms use their tentacles to collect tiny bits of food, like dead plants and animals, from the water or the ocean floor. These tentacles probably also work like gills, helping the worm breathe. The mouth and tentacles are at the very tip of the introvert. The introvert often has many small spines or bumps on it, while the trunk part of the body is usually smooth.

Images for kids

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  Sipunculus nudus

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  Lecthaylus gregarius, a sipunculan from the Silurian of Illinois.

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  A plate of Sipunculid worm jelly.

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  This sipunculid worm dish is made by adding vinegar and local spices. Taken in Cebu, Philippines.

See also

In Spanish: Sipuncúlidos para niños